Unit 2 Topic 1.6

Sensation

Sensation

The process by which our sensory receptors and nervous system receive and represent physical stimulus energies from our environment.

Threshold (absolute threshold)

The minimum intensity of stimulation needed for a person to detect a particular stimulus 50 percent of the time.

Transduction

The conversion of one form of energy, such as light waves or sound waves, into neural impulses that the brain can interpret.

Just noticeable difference

The minimum difference between two stimuli required for a person to detect a change 50 percent of the time.

Sensory adaptation

The diminished sensitivity to a prolonged, unchanging stimulus as a result of constant exposure.

Weber's law

The principle stating that to be perceived as different, two stimuli must differ by a constant minimum percentage rather than a constant amount.

Sensory interaction

The principle that one sense may influence or alter another, such as when the smell of food affects its taste.

Synesthesia

A neurological condition where the stimulation of one sensory pathway leads to involuntary experiences in a second, unrelated sensory pathway.

Vision

The biological faculty of sight, where the eyes detect electromagnetic light waves and translate them into visual images.

Retina

The light-sensitive inner surface of the eye containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.

Blind spot

The specific point on the retina where the optic nerve leaves the eye, creating a spot with no receptor cells where vision is absent.

Incomplete retinal images

The phenomenon where the physical image projected onto the retina is fragmentary, inverted, or blocked, requiring the brain to mentally fill in the gaps.

Lens

The transparent structure behind the pupil that changes shape to help focus incoming light rays onto the retina.

Accommodation

The process by which the eye's lens changes its curvature and thickness to focus near or distant objects on the retina.

Nearsightedness

A visual condition where nearby objects are seen clearly but distant objects appear blurry because the image focuses in front of the retina.

Farsightedness

A visual condition where distant objects are seen clearly but close objects appear blurry because the image focuses behind the retina.

Rods

Retinal receptors concentrated in the periphery that detect black, white, and gray, necessary for peripheral and twilight vision.

Light/dark adaptation

The chemical and neural adjustment process the eyes undergo to normalize vision when transitioning between bright light and darkness.

Color vision

The ability of the visual system to distinguish different wavelengths of light, allowing us to perceive various hues.

Trichromatic color theory

The theory that the retina contains three distinct types of color receptors (red, green, and blue) which, when stimulated in combination, produce the perception of any color.

Opponent-process color theory

The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision by exciting one color pathway while inhibiting its opposite.

Cones (blue/red cones in the retina)

Retinal receptor cells concentrated near the center of the retina that function in daylight, detecting fine detail and enabling color perceptions like red, green, and blue.

Afterimages

Visual sensations that briefly persist after the original stimulus has been removed, often displaying the complementary colors of the original image.

Ganglion cells

Specialized neurons in the retina whose axons bundle together to form the optic nerve, transmitting compressed visual data to the brain.

Fovea

The central focal point in the retina around which the eye's cones cluster, providing the absolute sharpest and clearest visual acuity.

Dichromatism

A form of partial color blindness where an individual has only two functioning types of cone receptors, making it difficult to distinguish between certain colors.

Monochromatism

A rare form of total color blindness where a person has no functioning cones (or only one type), perceiving the world entirely in shades of black, white, and gray.

Prosopagnosia

A neurological condition characterized by the inability to recognize familiar faces, even though general visual processing and intelligence remain intact.

Blindsight

A condition in which a person can respond to visual stimuli without consciously experiencing or seeing them, usually caused by damage to the brain's visual cortex.

Sound waves

Longitudinal waves of pressure changes that propagate through a medium like air, which our auditory system perceives as sound.

Wavelengths (pitch)

The distance between consecutive peaks of a sound wave, which determines the perceived highness or lowness of a tone.

Amplitude (loudness)

The physical height or intensity of a sound wave, which determines our psychological perception of volume.

Place theory (pitch perception)

The theory linking the pitch we hear with the specific physical location along the basilar membrane that is stimulated by a sound wave.

Volley theory (hearing)

The principle that groups of embryonic auditory nerve fibers fire neural impulses in rapid, alternating successions to achieve a combined frequency higher than any single neuron can manage.

Frequency theory (pitch perception)

The theory that the rate of nerve impulses traveling up the auditory nerve matches the exact frequency of a tone, enabling us to sense its pitch.

Hearing difficulties

A broad range of auditory impairments, including conduction deafness (damage to mechanical structures) and sensorineural deafness (damage to cochlear hair cells or the auditory nerve).

Conduction deafness

Hearing loss caused by physical damage to the mechanical structures of the outer or middle ear that conduct sound waves to the cochlea.

Sensorineural deafness

Hearing loss caused by damage to the cochlea's receptor hair cells or to the auditory nerve, preventing the transmission of neural impulses to the brain.

Pheromones

Airborne chemical signals released by an animal that unconsciously communicate message alerts or trigger specific behavioral and physiological responses in other members of the same species.

Chemical senses

The sensory modalities of gustation (taste) and olfaction (smell) that function by reacting directly to chemical molecules in the environment.

Olfactory system/bulb

The bodily structures responsible for smell, centering on a brain structure located above the nasal cavity that receives and processes chemical scent data bypassing the thalamus.

Gustation

The biological sense of taste, occurring when chemical molecules dissolve in saliva and stimulate receptors on the tongue.

Tastes (sweet, sour, bitter, salty, umami)

The five primary, evolutionarily distinct taste profiles recognized by human sensory receptors to identify nutrients and potential toxins.

Supertasters, medium tasters, and nontasters

The classification of individuals based on their density of tongue papillae, which dictates extreme sensitivity, standard sensitivity, or low sensitivity to tastes (especially bitterness).

Tongue

The muscular organ in the mouth covered in papillae that houses taste buds and manipulates food for chewing, swallowing, and speech.

Taste receptors

Specialized chemical receptor cells grouped inside taste buds on the tongue that bind with food molecules to generate taste signals.

Structures in skin (hot from warm/cold, pain)

A network of distinct cutaneous receptors, including free nerve endings and thermoreceptors, that detect mechanical pressure, temperature alterations, and damaging tissue stimuli.

Gate-control theory

The model proposing that the spinal cord contains a neurological "gate" that either blocks pain signals or allows them to pass through to the brain depending on competing nerve fiber activity.

Oleogustus

The distinct, evolutionarily adaptive chemical taste profile triggered specifically by unique fat molecules (long-chain fatty acids).

Sensory interaction

The principle that our senses regularly combine and modify one another, such as how scent and texture coalesce to generate a food's flavor.

Touch

The somatosensory system consisting of specialized skin receptors that detect physical pressure, warmth, cold, and noxious pain stimuli.

Vestibular sense

The biological sense of body orientation, equilibrium, and balance, heavily dictated by fluid movement inside the inner ear.

Phantom limb syndrome

A psychological and neurological phenomenon where an individual continues to experience vivid sensations, tingling, or intense pain originating from an amputated limb.

Semicircular canals

Three fluid-filled, loop-like structures in the inner ear that detect rotational head movements to help maintain physical balance.

Kinesthesis

The sensory system that tracks the position, orientation, and physical movement of individual body parts via receptors located in muscles, tendons, and joints.